JSFiddle - React, Tailwind, and code Playground

HTML

<div id="rack1" class="rack">
    <span id="rackunit1" class="rackspace">
        <span id="component1">BoxA</span>
        <span id="label1">Space A</span>
    </span>
    <span id="rackunit2" class="rackspace">
        <span id="label2">Space B</span>
    </span>
    <span id="rackunit3" class="rackspace">
        <span id="component2">BoxA</span>
        <span id="label3">Space C</span>
    </span>
</div>
<div id="rack2" class="rack">
    <span id="rackunit4" class="rackspace">
        <span id="component3">BoxC</span>
        <span id="label4">Space D</span>
    </span>
    <span id="rackunit5" class="rackspace">
        <span id="label5">Space E</span>
    </span>
    <span id="rackunit6" class="rackspace">
        <span id="component4">BoxD</span>
        <span id="label6">Space F</span>
    </span>
</div>

JavaScript

$(".rack .rackspace:not(:has(span[id^=component]))").css("color", "#ff0000");